Hi Pelin, I second what Daisy said. The first sentence is incorrect, as it mixes time reference. It is the second conditional, the form of which is "If +simple past, then would + simple present, like, "If I had a 10 million dollars, I would travel the world." The first sentence DOES follow the form, but in this particular case, the thing refers to something that was seen in the past, as opposed to using the simple past to indicate a hypothetical situation for the present. The second sentence is correct, but is known as a mixed conditional. "I wouldn't believe it" is the independent clause of the second conditional, and means that you wouldn't believe the thing based on some previous condition. In this case, that previous condition, "if I hadn't seen it with my own eyes," means something that was seen in the past. This is different from using the simple past, as one would normally do in the second conditional, to indicate a hypothetical of not seeing something in the present. More specifically, this second sentence mixes the independent clause of the second conditional with the dependent clause of the third conditional. Mixed conditionals are very challenging and require a firm grasp of the four main conditionals before they can be fully understood. The third sentence is also correct, as it is the third conditional, also called the unreal past. The form is if+subject+had+third form of the verb then subject+would+have+third form of the verb. Example: "If he had studied harder, he would have passed the exam." It is called the unreal past because the condition for the thing to have happened in the past was not satisfied. He did NOT study harder, so he did NOT pass the test. Conditionals can be challenging. I wish you the best of luck!